As far as what you said is concerned, you do not suffer losses, but you might as well try legal channels. 1, you can find the person who sells the keyboard, let him make a statement or something, or let him testify in court; 2. You can find another buyer and then prove that the buyer and the promoter are a group; But these two kinds of difficulties are relatively large. If it is really "framed", it is basically hopeless. You can respond to the lawsuit, but don't admit the facts and let the court decide.